Magnetoresistive Element With BCC Buffer Layer
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Solution Overview
Problem
Current magnetoresistive elements, particularly CPP type, face challenges in achieving high magnetoresistive ratios due to low resistance values and limited spin-dependent conduction, which restricts their output and sensitivity in reading magnetic signals from recording media, especially under low relative speeds.
Innovation Solution
Incorporating a body-centered cubic layer with a thickness of 2 nm or more in the magnetoresistive film and using a resistance adjusting layer with insulating and high-quality metal paths to enhance spin-dependent scattering, while controlling grain size and crystal orientation to optimize magnetic characteristics and resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spin-valve structure is used in a CPP magnetoresistive element, then the magnetoresistive ratio can reach about 10 times that of CIP type, but the total thickness of spin-dependent layers is very small and the number of interfaces is few, resulting in low resistance value and low absolute output
Solution Approach 1:
The buffer layer is segmented into three distinct sub-layers (first buffer layer, second buffer layer, and third buffer layer) with different materials and functions. This segmentation allows each sub-layer to contribute differently to spin-dependent scattering, thereby increasing the total resistance while maintaining the spin-valve structure's high magnetoresistive ratio.
Solution Approach 2:
The buffer layer uses composite materials including Ta, (Ni100-xFex)100-yCry alloy, and Cu in a stacked configuration. These composite materials provide different spin-dependent scattering properties, enabling the buffer layer to contribute significantly to the overall resistance while maintaining structural integrity and magnetic properties.
2Adaptability or versatility
If the thickness of ferromagnetic layers is reduced to 5 nm to achieve low magnetic field saturation, then the magnetoresistive effect is enhanced, but the resistance value and absolute output remain too low for practical application
Solution Approach 1:
Different regions of the magnetoresistive element are assigned different qualities: the ferromagnetic layers maintain thin thickness (5 nm) for low magnetic field saturation, while the buffer layer is designed with thick composite structure for high resistance. This local quality differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The buffer layer acts as an intermediary between the pinned layer and the free layer. It provides additional spin-dependent scattering interfaces without directly participating in the magnetic switching process, thereby increasing resistance while allowing the thin ferromagnetic layers to maintain their low-field saturation capability.
3Measurement precision
If a resistance adjusting layer containing insulator is inserted in the spin-valve film to enhance magnetoresistive ratio, then Rsd becomes greater than Rsi, but the current confinement effect limits the effectiveness to only the vicinity of the resistance adjusting layer
Solution Approach 1:
The buffer layer performs multiple functions simultaneously: it serves as a structural support layer, provides spin-dependent scattering interfaces to increase resistance, and maintains the magnetic properties of the spin-valve structure. This multi-functionality eliminates the need for separate resistance adjusting layers, simplifying the overall structure while achieving the same effect.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases the magnetoresistive ratio and coercivity, enabling higher sensitivity and output for magnetoresistive elements, making them suitable for advanced magnetic recording and reading applications.
Implementation Method 1
The magnetoresistive element includes two types of structures, that is, a CIP (current-in-plane) type adapted to flow a sense current in a parallel direction to the film plane of the element, and a CPP (current-perpendicular-to-plane) type adapted to flow a sense current in a perpendicular direction to the film plane of the element. The CPP magnetoresistive element has been reported to show a magnetoresistive ratio of about 10 times that of the CIP magnetoresistive element
Implementation Method 2
The resistance adjusting layer includes a portion of an insulator where a current does not flow, and low-resistance portions (metal paths) through which the current flows. The current is confined toward the metal paths in the vicinity of the resistance adjusting layer. This is called a current confinement effect.
Implementation Method 3
With regard to the two ferromagnetic layers sandwiching a nonmagnetic layer (referred to as a 'spacer layer' or an 'intermediate layer'), the magnetization of one ferromagnetic layer (referred to as 'pinned layer' or 'magnetization pinned layer') is pinned by applying an exchange bias magnetic field
Implementation Method 4
the magnetization of the other ferromagnetic layer (referred to as 'free layer' or 'magnetization free layer') can be reversed by an external magnetic field (for example, signal magnetic field)
Data Source
AI summary
A magnetoresistive element includes a magnetoresistive film having a magnetization pinned layer whose magnetization is substantially pinned to one direction, a nonmagnetic intermediate layer, and a magnetization free layer whose magnetization is changed in direction depending on an external magnetic field, in which the magnetization pinned layer or nonmagnetic intermediate layer includes an insulator, and a pair of electrodes electrically connected to the magnetoresistive film so as to supply a sense current in a direction substantially perpendicular to a plane of the magnetoresistive film. The magnetization free layer includes a body-centered cubic layer with a body-centered cubic structure, and the thickness of the body-centered cubic layer is 2 nm or more.